Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
FOCUSED NARROW BEAM COMMUNICATION SYSTEM
BACKGROUND OF THE INVENTION
(1) Field of the invention
This invention relates to line-of sight wireless communication systems for
microwave and millimeter wave communication, and more particularly to a
wireless
communication system for point-to-point or point-to-multipoint communication
which
uses a dielectric material lens antenna to focus received or transmitted
information
carrying radio frequency (rf) signals.
(2) Description of related art
The design of many radio frequency (rf) communication systems is based on
stationary reflective, parabolic antennas. Such antennas are capable of
transmitting and
receiving narrow beam rf signals. A major disadvantage of such antennas is
that they are
not directionally agile. Such antennas can only transmit signals in one
direction. This
means that a communication system based on parabolic antennas typically has a
series of
antenna arrays, each array comprising a plurality of antennas for receiving
incoming
signals, and another plurality of antennas for transmitting signals to the
next antenna
array. These systems are typically used for transmitting signals over long
distances.
Another type of wireless communication system is cellular communication. For
cellular communication between a first communication device and a second
communication device within a cell, the communication devices broadcast and
receive
signals from and to a base station. The frequency of the signals broadcast
from the base
station and the frequency of the signals received by the base station are
different. The
different frequencies allow for simultaneous reception and transmission of
information by
a communication device. The ability to simultaneously receive and transmit
information in
one device is called duplex communication.
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The base station of a cellular cell typically comprises an antenna array
having
circuitry and computer control for receiving incoming signals, for
transforming the signals
without losing the information carried by the received signals, and an array
of transmit
antennas for transmitting the transformed signals to another communication
device.
Typically, each antenna is a dipole antenna. A major disadvantage of the
transmit
antennas currently used is that the antennas broadcast omnidirectionally. A
more efficient
communication system can be established if the transmit antennas are capable
of beaming
a signal directly to a desired receiver or receivers.
In wireless communications, signal fading is a major problem. Minimizing or
eliminating the effects of fading is important to successful free-space
communication.
Some methods for curing the fading problem are space diversity, frequency
diversity, time
diversity, and polarization diversity broadcasting.
In wireless communications it is also desirable to be able to accommodate a
large
number of simultaneous users without a loss in signal quality due to
interference from
i 5 other information signals. Several methods for increasing the number of
users that can
use a communication system at the same time have been developed. Among these
methods are frequency division multiplexing, time division multiplexing, code
division
multiplexing, and space division multiplexing.
In wireless communication, it is desirable for a base station to have a beam
forming antenna. A beam forming antenna is an antenna that has the capability
to form
multiple rf beams which can be directed beams in selected directions. With
such a
capability, the base station and adjacent base stations can employ frequency
reuse.
Frequency reuse is the ability of a base station and adjacent base stations to
use the same
frequency to communicatively connect different users in separate communication
systems
without interference due to the use of the same frequency. The ability to
employ
frequency reuse increases the number of users who can use a communication
network.
With current cellular communication systems, frequency reuse is employed in
cells that
are separated by a sufficient distance so that the signals from a first cell
using a particular
frequency will not interfere with the signals of another cell using the same
frequency.
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With beam forming antenna, frequency reuse can be utilized within a cell and
between
adjacent cells.
U.S. Patent No. 5,485,631, issued to Bruckert describes a multiple sectorized
antenna system which achieves a low reuse factor. The reuse factor
characterizes the
proximity of the closest base station which can reuse a particular frequency.
U. S. Patent
No. 5,260,968, issued to Gardner et al., describes a communication system
which uses a
multiple array antenna and space division multiplexing. U.S Patent No.
4,819,227, issued
to Rosen, shows beam forming for frequency reuse in satellite communication
systems.
Again, the system uses a multiple antenna array for beam forming. U. S. Patent
No.
4,730,310, issued to Acampora et al., shows a communication system which uses
a large
main reflector or a phased array antenna in conjunction with time division
multiplexing to
provide a communication system capable of frequency reuse within a
communication cell.
A key aspect of the present invention is the use of a dielectric material lens
in a
communication system to focus received or transmitted rf signals which pass
through the
lens. Such lenses have been used in other arts for many years. The lenses have
been used
as passive reflectors, and as antennas in radar systems involving navigation
and aircraft
landing. U.S. Patent No. 3,703,723, issued to Albanese et al., describes a
Luneberg lens
used as a passive reflector. U.S. Patent No. 4,287,519, issued to Doi,
describes a
Luneberg lens used as an antenna system which takes the place of three
separate high gain
antennas. U.S. Patent No. 4,031,535, issued to Isbister, describes a multiple
frequency
navigation radar system for determining the location and identification of
navigational
markers.
U. S. Patent No. 4,806,932, issued to Bechtel, describes a radar-optical
transponding system for use in aircraft landing systems. A transceiver on an
aircraft sends
a signal to a ground based lens. The lens focuses the signal onto a
transponder array,
which adds identifier information and meteorological data to the signal and re-
transmits
the signal back to the aircraft's transceiver. The signal transmitted to the
aircraft is used
to guide the aircraft.
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SUMMARY OF THE INVENTION
(1) Progressive contribution to the art
We have invented a communication system for point-to-point or point-to-
multipoint communication which uses a dielectric material lens antenna to
focus received
or transmitted rf energy. The communication system is capable of serving
multiple users
and of handling multiple simultaneous communication links between various
users. The
communication system can be designed so that the lens is used only to transmit
rf signals.
Alternatively, the communication system can be designed so that the lens is
capable of
simultaneously transmitting and receiving rf signals. The lens is
directionally agile, and is
capable of receiving and transmitting signals throughout a 360 degree area
surrounding
the lens.
When used to receive rf energy, the dielectric material lens focuses incoming
rf
signals onto signal processing equipment. When used to transmit rf energy, the
dielectric
material lens focuses outgoing rf signals into narrow beam signals which are
transmitted
directly to a desired receiver or receivers.
The lens and signal processing equipment can be directly connected to a
communication device, or the lens and signal processing equipment can act as a
repeater,
also called a base station. If the lens and signal processing equipment are
directly
connected to a communication device, signals received by the lens are fed to
the signal
processing equipment, and the resulting signal is sent to a user interface.
Output signals
from the user interface are processed by the signal processing equipment and
sent to the
lens where the signals are broadcast as narrow beam rf signals directly to a
second
communication device or communication devices.
If the lens and signal processing equipment are used as repeater, a first
communication device broadcasts rf signals to the lens, and the lens sends the
signals to
the signal processing equipment. The signal processing equipment sends
processed
signals back to the lens which broadcasts the signals as narrow beam rf
signals directly to
a second communication device or communication devices.
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A lens and corresponding signal processing equipment can be used to
simultaneously establish many separate communication systems between various
users.
(2) Objects of this invention
An object of this invention is to provide a wireless communication system
which
uses a dielectric material lens to focus transmitted rf signals into narrow
beam rf signals.
Another object is to provide a wireless communication system which uses a
dielectric material lens to focus received rf signals onto signal processing
equipment.
Another object is to provide a communication system which uses a lens to
broadcast narrow beams of rf signals directly to a desired receiver or
receivers.
Another object is to provide a wireless communication system capable of
providing point-to-point or point-to-multipoint duplex communication for a
large number
of simultaneous users.
Another object is to provide a communication system which is capable of using
frequency diversity, space diversity, or polarization diversity broadcasting
to eliminate or
minimize the problem of signal fading.
Another object is to provide a communication system which is capable of using
code division multiplexing, time division multiplexing, frequency division
multiplexing or
space division multiplexing to increase the maximum number of simultaneous
users that
the communication system can accommodate.
Another object is to provide a communication system which can employ frequency
reuse to increase the number of simultaneous users that the communication
system can
accommodate.
Another object is to provide a local area network communication system.
Another object is to provide a lens and signal processing equipment which can
be
used as a base station of a cellular network.
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Further objects are to achieve the above with a system which is sturdy,
compact,
durable, simple, safe, efficient, versatile, ecologically compatible, energy
conserving and
reliable; yet is inexpensive and easy to manufacture, install, maintain and
use.
The specific nature of the invention, as well as other objects, uses, and
advantages
S thereof, will clearly appear from the following description and from the
accompanying
drawings, the different views of which are not necessarily scale drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a communication system between a direct connected
communication device, a base station, and a third communication device.
FIG. 2 is a diagram of a cellular network where separate cells are represented
pictorially as hexagons.
FIG. 3 is a diagram of a point-to-multipoint communication system.
FIG. 4 is a diagram of the beam focusing pattern of received and transmitted
rf
energy for a spherical Luneberg lens where one focal point is located on the
surface of the
sphere and the other focal point is located at infinity.
FIG. 5 is a diagram of a constant-K lens fed with end-fire feeds.
FIG. 6A is a front view of a convex shaped dielectric lens.
FIG. 6B is a side view of a convex shaped dielectric lens.
FIG. 7 is a view of a spherical dielectric material lens with a partial cut
away of
the array of feed devices.
FIG. 8 is a block diagram of a receive module.
FIG. 9 is a block diagram of a transmit module for a direct connected
communication device.
FIG. 10 is a block diagram of a transmit module for a base station.
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As an aid to correlating the terms of the claims to the exemplary drawings the
following catalogue of elements is provided:
communication system
S 12 communication device
14 dielectric material lens
16 signal processing equipment
17 narrow beam signals
18 direct connected communication
device
10 19 omnidirectional signals
user interface
22 coaxial cable
24 base station
26 received signals
1 28 end-fire antenna
S
convex shaped lens
3 2 array
34 feed device
36 receive module
20 38 transmit module
cross connect
42 duplex switch
44 controller
46 low noise amplifier
25 48 mixer
SO oscillator
52 amplifier
54 band-pass filter
56 amplifier
30 57 signals from receive module
58 gain control
60 amplifier
62 gain control
64 mixer
35 66 oscillator
68 amplifier
70 mixer
72 supervisory signals
74 band-pass filter
40 76 amplifier
78 output signals
79 signals from user interface
80 information
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82 information
84 connector
86 broadcast station
88 switching station
S 90 other type of communication
system
92 tower
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the drawings, and in particular to FIGS 1, 2, and 3 a
communication system is designated generally as 10. The communication system
is
comprised of at least two communication devices 12, with at least one of the
communication devices having a lens antenna 14. The lens antenna is comprised
of a
dielectric material lens 15, and signal processing equipment 16. The lens
antenna can be
used to transmit and receive radio frequency signals as shown in FIGS 1 and 2.
In a
second embodiment of the invention, as shown in FIG. 3, the lens and signal
processing
equipment are used only to transmit rf signals as narrow beams directly to
another
communication device or communication devices.
As indicated in the drawings, each communication device is given an individual
alphanumeric designation. For example, 12a and 12b are two distinct
communication
devices. Also, information carrying signals that are received by or
transmitted to a
communication device are given alphanumeric designations, where the alphabetic
character indicates the transmission source of the signal. For example, rf
signal 17b is a rf
signal that was transmitted from communication device 12b. The information
carried in
an input or output rf signals can be voice or data information; or the
information can be
the signal itself, for example, a distress signal.
A communicative connection formed by rf signals transmitted between a
communication device 12 , a lens antenna 14 and another communication device
12 forms
a communication system. A communication network is formed by all of the
communication systems which can connect various users together. As shown in
FIGS 2
and 3, several individual communication devices 12 can be used to create the
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communication network used to communicatively connect a first communication
device
to a second communication device.
The communication devices 12 are devices which are capable of transmitting
and/or receiving radio frequency signals. Some examples are cellular phones;
pagers; and
computers, televisions, automatic teller machines, and other electronic
equipment which is
connected to a transmitter and/or a receiver. Also, a lens antenna 14 of this
invention or
a base station of a cellular network is a communication device 12.
The lens antenna 14 can be a component of a communication device 12 that is
directly connected to the communication device. Such direct connected
communication
devices 18, as shown in FIG. 1, are comprised of a lens 15, signal processing
equipment
16, and user interface 20. The user interface is directly connected to the
signal processing
equipment by any conventional means; such as coaxial cable 22, fiber optic
cable, or
wiring.
Alternatively, the lens antenna 14 can be base station 24. As shown in FIG. 1,
the
base station, also designated as 12b, functions as a relay or repeater between
two separate
communication devices 12a and 12c. The base station communicatively connects
communication device 12a to communication device 12c by narrow beam rf signals
17.
The dielectric material lens 15 is preferably a variable refractive index
lens, such as
a Luneberg lens. FIG. 4 shows a diagram of the beam focusing pattern of
received and
transmitted rf energy for a spherical Luneberg lens.
A dielectric material lens 15 made of a material having a constant refractive
index
may be used as a somewhat optically degraded substitute for a variable
refractive index
lens. Such a lens is a constant dielectric constant (constant-K) lens and is
shown in
FIG. 5. The lens has focusing properties similar to those of a variable
refractive index
lens, but small aberrations in the resulting focused beam are present. Such
aberrations are ,
small for most practical applications and have negligible effect. For a
constant-K lens, the
dielectric constant should be within the range of approximately 2.0 to 3.5.
Some of the
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aberrations of such a lens are diminished when the lens is fed by dual
frequency end-fire
antenna 28, as shown in FIG. 5.
A lens 15 used in the communication system 10 of the present invention is
preferably spherical, but other shapes can be used for specific applications.
The lens
should have a shape wherein at least one surface of the lens is a quadric
surface. For
example, a convex shaped lens 30, as shown in FIG. 6A and 6B, can be used if
full 360°
directional agility is not desired or required. One application for such
lenses is in long
distance rf signal transmission systems.
The directivity and beam width of a focused beam 17 output from a lens 15 can
be
controlled by modifying the illumination taper and by radially adjusting the
effective phase
center of feed device 34 with respect to the focal point of the lens. The beam
width of a
signal broadcast through the lens is also a function of the wavelength of the
signal, and of
the diameter of the lens.
As shown in FIGS 1 and 7, the signal processing equipment 16 comprises array
32
of feed devices 34, receive modules 36, transmit modules 38, cross connect 40,
duplex
switch 42, and controller 44. The number and positioning of the feed devices
of the feed
device array surrounding the lens 15 determines the directional range of the
communication system. Preferably, the feed device array encircles the lens,
providing a
full 360° directional range. Typical feed devices include small
aperture waveguide horns,
open end waveguides, dielectric-loaded waveguides, patch antennas, and end-
fire
antennas. The array can be made of a combination of types of feed devices, for
example,
the array could be comprised of dual frequency patch antennas covering a
portion of the
lens, and rf horns covering another portion of the lens. Preferably, the feed
devices are
patch antennas so that the feed devices do not block a signal from passing
through and
beyond the lens. When a feed device broadcasts a signal through the lens, the
signal is
focused into a narrow beam signal which occupies a fixed solid angle in space.
Receive modules 36 and transmit modules 38 are connected to each feed device
34 of the feed device array 32. A single transmit module and a single receive
module can
be used to feed and receive to and from the feed device array, but it is
preferable to have
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several interconnected receive and transmit modules, so that a receive module
and a
transmit module handle only a portion of the feed device array. The exact
number of
receive or transmit modules required is a function of the user load that the
lens handles.
A receive module 36 receives focused receive signals 26 that were fed to a
feed
device 34 from the lens 15. FIG. 8 shows a block diagram of a basic embodiment
of the
receive module circuitry. The received signals from the lens are routed to low
noise
amplifier 46. The amplified signals are sent to mixer 48. Reference signals
which are
generated by oscillator 50 and amplified by amplifier 52 are also sent to the
mixer 48.
The mixer product is sent to band-pass filter 54 to filter out unwanted mixer
products.
The resulting signals are sent to amplifier 56. Gain control signals from gain
control 58
control the gain of amplifier 56. Resulting signals 57 are passed to a
transmit module 38
if the communication device is a base station 24, or the resulting signals are
passed to a
user interface 20 if the communication device is a direct connected
communication device
18.
A transmit module 38 sends output signals 78 to a feed device 34. FIG. 9 shows
a
block diagram of a basic embodiment of the transmit module circuitry for a
direct
connected communication device 18. Signals 79 from the user interface 20 are
sent to
amplifier 60. Gain control signals from gain control 62 control the gain of
the amplifier
60. The signals from the amplifier 60 are sent to mixer 64. The mixer 64 is
also fed with
reference signals which are generated by oscillator 66 and amplified by
amplifier 68. The
resulting signals are sent to mixer 70. Mixer 70 is also fed with supervisory
signals 72
from controller 44. The resulting signals are sent to band-pass filter 74. The
signals are
then sent to amplifier 76, which generates output signals 78.
FIG. 10 shows a block diagram of a basic embodiment of transmit module
circuitry for a base station 24. Input signals 57 from the receive module are
sent to mixer
64. The mixer 64 is also fed with reference signals which are generated by
oscillator 66
and amplified by amplifier 68. The resulting signals are sent to mixer 70.
Mixer 70 is also
fed with supervisory signals 72 from controller 44. The resulting signals are
sent to band-
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pass filter 74. The signals are then sent to amplifier 76, which generates
output signals
78.
As shown in FIG. 1, and regardless of whether the communication device 12 is a
base station 24 or a direct connected communication device 18, output signals
78 from
the amplifier 76 of the transmit module 38 are sent through the duplex switch
42, the
cross connect 40, and a feed device 34. The feed device transmits the signals
to the lens
15, which converts the signals to narrow beam rf signals 17. A cross connect
and/or a
duplex switch are not necessary for all applications.
The transmit module 38 adds supervisory signals 72 to the signal stream in the
transmit module. The supervisory signals are supplied to the transmit module
by the
controller 44. Typically, the supervisory signals contain information relating
to the source
and destination of the signal, as well as identification of the device 12 that
has most
recently broadcast the signal. This information is used to ensure that a
signal is broadcast
to a desired location. If a lens antenna 14 receives signals which do not have
supervisory
1 S signals indicating that the signals are sent to the lens antenna which
received the signals,
the signal processing equipment 16 will not process the signals.
The cross connect 40 allows the controller 44 to direct the output signals 78
from
a transmit module 38 to the proper feed device 34 or feed devices that will
ensure that the
output rf signals from a lens 15 will reach the proper destination.
For a communication system 10 where the lens antenna 14 are used only to
transmit signals to other devices 12, as shown in FIG. 3, the controller 44
for broadcast
station 86, and the controller 44 for any base station 24 that receives the
broadcast
signals, stores location information for all devices that are to receive
narrow beam signals
17 transmitted from the broadcast station or base stations. The location
information is
used by the controller 44 and the cross connect 40 to ensure that output
signals 78 are fed
to the proper feed device 34 or feed devices so that desired communication
devices 12
will receive the narrow beam signals 17 transmitted from the broadcast station
86 or base
stations 24.
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As shown in FIG. I, in a communication system 10 in which all communication
devices 12 of the system receive and transmit rf signals, a first
communication device,
such as 12b, transmits signals 78 through the same feed device 34 which
received signals
19a from a second communication device 12a. In this type of system, the cross
connect
40 and controller 44 direct output signals 78 through the same feed device
which receives
signals from the communication device being transmitted to. This eliminates
the need for
storing information relating to the location of communication devices within a
communication network.
The duplex switch 42 prevents output signals 78 from being received by the
feed
device array 32 and being re-processed by the signal processing equipment 16
when the
output signals 78 are broadcast through the lens 15. If the lens antenna 14 is
used only to
transmit rf signals, a duplex switch is not needed.
The controller 44 provides the supervisory signals 72 to the transmit module.
The
controller in conjunction with the cross connect 40 determines which feed
device 34 of
I S the feed device array 32 the output signals 78 are sent to so that the
corresponding
narrow beam rf signals 17 that are broadcast from the lens 15 will reach a
desired
communication device 12.
The circuitry of the receive and transmit modules 36, 38 and of the controller
44
can incorporate systems for minimizing the effect of signal fading, and for
increasing the
number of users who can simultaneously use the communication system. Space
diversity,
time diversity, frequency diversity, and polarization diversity circuitry can
be incorporated
in the signal processing equipment to minimize the effect of signal fading.
Also, time
division multiplex, frequency division multiplex, polarization division
multiplex, code
division multiplex and space division multiplex circuitry can be incorporated
in the signal
processing equipment to increase the number of users who can simultaneously
use the
communication system. Such circuitry is known in the art of cellular
communication and
is not described in detail here.
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The electronic sub-systems that comprise a receive module 36 and/or a transmit
module 38 can be made from separate components, or the components can be
combined
onto an integrated circuit, such as a monolithic microwave integrated circuit.
The lens 15 of a direct connected communication device 18, or the lens 15 of a
base station 24 forms narrow beam rf signals 17 which are transmitted to
desired
communication devices 12. Because the beams are narrow and directionally
oriented,
adjacent cells in a cellular network can reuse some of the frequency spectrum
used by
communication devices which broadcast narrow beam signals in a neighboring
cell as long
as the narrow beam signals do not overlap and interfere with each other. This
is known as
frequency reuse. Frequency reuse by a single lens antenna 14 can be
accomplished by
using polarization division multiplexing, space division multiplexing, code
division
multiplexing, or time division multiplexing to broadcast separate signals on
the same
frequency.
As noted above, a communication system 10 is comprised of at least two
1 S communication devices 12, at least one of which has a dielectric material
lens 15 and
signal processing equipment 16. The dielectric material lens focuses received
and
transmitted rf signals. Signals transmitted and/or received by the lens are
processed by
the signal processing equipment. Such communication systems are shown in FIGS
1, 2,
and 3.
FIG. 1 shows a direct connect communication device 18 which is communicatively
connected to a base station 24, which in turn is communicatively connected to
another
communication device 12a. In FIG. 1, the direct connect device is indicated
generally as
12c and the base station is indicated generally as 12b. The communication
device 12c
broadcasts omnidirectionally as indicated by reference numerals 19.
As shown in FIG. 1, direct connect communication device 18 is connected
directly
to the lens antenna 14. In this embodiment, received rf signals carrying
information 80
are focused by the lens 15 onto the signal processing equipment 16. The signal
processing equipment receives signals 26 from the lens. The information
contained in the
signals 26 is sent from the signal processing equipment to user interface 20
of the
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communication device. Output signals 79 from the user interface, which carry
information 82, are sent to the signal processing equipment. The output
signals 78 from
the signal processing equipment are passed through the lens and broadcast as
narrow
beam rf signals 17 to another communication device, which is base station 24
in FIG. 1.
Also as shown in FIG. I, a lens antenna 14 can function as a base station 24.
A
communication device 12c broadcasts input rf signals, which carry information
82, to the
lens 15 of the base station. The lens focuses the received signals 26 onto the
signal
processing equipment 16. The signal processing equipment processes the
received
signals, and sends output signals 78 back to the lens. The output signals are
passed
through the lens and broadcast as narrow beam rf signals 17 which still carry
the
information 82. The narrow beam signals are transmitted to another
communication
device, 12a as shown in FIG. 1.
The communication systems between the three communication devices 12a, 12b,
and 12c in FIG. 1 form a full duplex communication network. The direct connect
communication device 18 receives information 80 at the same time that it
broadcasts
information 82. Likewise, communication device 12a receives information 82 at
the same
time that it broadcasts information 80. The base station 24 functions as a
relay or
repeater between the other two communication devices. The base station 24 of
FIG. 1
connects communication device 12a to communication device 12c. The base
station can
simultaneously connect many other communication devices together.
FIG. 2 shows a cellular network where the base stations are referenced as 24 a
- f.
Central switching station 88 can connect to other types of communication
networks, such
as a wire or cable connected communication system, or a long distance rf
signal
transmission system. This is represented in FIG. 2 by reference number 90.
Also, the
central switching station is interrogated by the base stations to determine
the target
locations of desired communication devices 12 and the most efficient route for
sending
signals to the desired communication devices. For example if communication
device 120
which is served by base station 24b is used to communicate with communication
device
12p, which is served by base station 24f, the switching office could route the
communication through base station 24d, as shown, or base station 24e. Also,
if one of
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the base stations used in a communication link fails or becomes overburdened,
the
switching office can re-route communication traffic through other base
stations.
Generally, a communication device 12 has a transmitter and a receiver,
although
there are applications where a communication device is not required to have
both a
transmitter and a receiver. For example, a point-to-multipoint wireless
communication
system 10 can be used to broadcast signals to many different receivers 12, as
shown in
FIG. 3. The lens antenna 14 receives signals from broadcast station 86. The
station can
be directly connected to the lens antenna by connector 84, as shown in FIG. 3,
or the
station can transmit rf signals to the signal processing equipment 16. The
broadcast
station broadcasts signals through the lens as narrow beam signals 17 to each
of the
receivers. The broadcast station 86 does not receive signals, so the broadcast
station does
not have a receive module 36, or a duplex switch 42. Since the receivers 12 do
not
broadcast information back to the broadcast station, the receivers are not
equipped with
transmitters. The number of users who can receive the signals broadcast by the
broadcast
station can be greatly increased if the signals are broadcast to several base
stations 24,
which in turn re-transmit the signals as narrow beam signals to various users.
As shown in FIG. 3, a communication device 12c may receive narrow beam
signals 17 from two or more different lens antennas 14. In FIG. 3,
communication device
12c receives signals 17a and 17d. The circuitry (not shown) of the
communication device
would be able to distinguish the best signal and use that signal.
Alternatively, the
communication device could use both signals. Also, the signals I7a and 17d
received by
communication device 12c would not necessarily have to carry the same
information.
FIG. 3 shows a point-to-multipoint communication system in which the lens 14
and signal processing equipment 16 are used for transmission only. A system
can be
designed so that the lens and signal processing equipment can accommodate both
transmission and reception of signals in a point-to-multipoint system by
including receive
modules 36, transmit modules 38, and duplex switches 42 in the signal
processing
equipment of each lens 14 which is to receive and transmit; and by having
transmitters and
receivers in each communication device which receives the originally broadcast
signals.
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To establish a communication system in an isolated local area network, the
controller 44 can store information concerning the location of all the
communication
devices 12 within the network and broadcast signals directly to desired
communication
devices. As an alternative, an inquiring communication device can broadcast an
inquiry
signal throughout the directional range of the lens antenna 14. The inquiry
signal when
received by the desired communication devices would cause the desired
communication
devices to send response signals back to the inquiring lens. The inquiring
communication
device can then transmit signals through the feed devices 34 which received
the response
signals. This establishes a direct communication system between the inquiring
communication device and a second communication device. Establishing a
communication system in a cellular network is well known in the art of
cellular
communication and is not described here.
When the location of the target receiver is determined, the controller 44 will
direct
output signals 78 from the transmit module 38 to a feed device 34. The feed
device
transmits to the lens, which will cause the output signals to be broadcast as
narrow beam
rf signals 17 to the desired communication device 12. The same signal can be
transmitted
to more than one feed device if point-to-multipoint communication is desired.
Also, if the
target communication device 12 is mobile, or if the lens antenna 14 is mobile,
the output
signals 78 to a communication device 12 can be directed by the controller 44
out of the
feed device 34 which last received input signals from the communication device
12.
When the signals transmitted to the lens antenna 14 are focused by the lens
onto more
than one feed device 34 of the feed device array 32, each feed device that
received the
signals from the communication device I2 is used to broadcast a narrow beam
signal to
the communication device.
The invention relates to line-of sight microwave and millimeter wave
communication. To increase the coverage area for a particular lens 14, the
lens should be
positioned as high as possible. Stationary lenses are preferably mounted on
towers 92.
The lenses of a local area network can be positioned anywhere as long as there
are no
obstructions which block the possible rf signals paths between the various
lenses of the
network. A plurality of lenses and the corresponding signal processing
equipment 1b of
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each lens can be networked together by cable or other means to increase the
information
handling capacity of a lens or to provide a way of bypassing an obstruction
which blocks a
specific directional range. Also, a lens 14 with signal processing equipment
16 can be
mounted on a satellite to provide an extended area of coverage for a network.
The communication systems as described above allow for point-to-point
communication or point-to-multipoint communication. A lens 14 and
corresponding
signal processing equipment 16 can be used to simultaneously establish many
separate
communication systems between many users. For example, in FIG. 2, base station
24b is
used to simultaneously establish communication systems and networks between
communication devices 12o and 12p; 12g and 12h; and 12i and 12j.
There are many possible uses for this invention, including but not limited to
the
following:
1. Microwave Telecommunications: The small size, low power, and low
costs of this technology provide the opportunity to establish a much more cost
effective
1 S microwave telecommunications system than exists today. A microwave
telecommunications system based on the microwave lens antenna could be
installed in a
developing country for a fraction of the cost of the current technology. Also,
the
microwave lens antenna could be used to replace the aging system of microwave
communications devices, which reside in the towers covering the face of the U.
S.. The
communication system can transmit verbal or digital data at rates which
significantly
exceed older microwave transmission capabilities.
2. Local Computer Networking: The microwave lens antenna technology
can transmit data in the megabytes per second range, a quantum leap over the
28,800 bps
Baud Modem available to computer networking today. Colleges, universities,
research
facilities, industry, police, etc. have requirements to link computer systems
between
facilities on a mission basis. This computer networking is currently
accomplished by
either laying specialized cables (expensive, time-consuming, and often
impractical) or by
linking through the telephone modem (slow data transfer). A small 6 inch
diameter
version of the microwave lens antenna can be linked by simply achieving a line-
of sight
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within a range of 75 miles. Each user can establish a security code that would
ensure that
the point-to-point communication was secure. The high data transmission rates
can
effectively link computers and projects with real-time data transfer.
3. Anti-collision Device for Automobiles: Considerable effort has been
expended on the study of the use of millimeter wave sensors for use in auto
anti-collision
systems. General Motors has been a leader in this field. Millimeter wave radio
frequencies, particularly those in the range of 96 Gigahertz (GHz), have been
chosen over
lower frequencies, primarily because they can be focused into a smaller
effective
beamwidth than is possible at the presently more widely used Ka-band
(approximately 35
GHz). However, the cost of components and assembly for a system operating at
96 GHz
are many more times more expensive than those operating at 35 GHz.
The Luneberg lens and the constant-K lens are capable of focusing high
frequency
radio waves much more effectively than conventional antennas, such as horns
and
parabolic antennas, in smaller sizes. Thus, the use of a Luneberg lens to
focus 35 GHz
may well result in a much less expensive anti-collision system.
4. Utility Meter Reading: The communication technology described herein
consists of a compact microwave interrogation unit that can focus a signal
into a beam
width of 2 degrees or less by means of a lens. This focused beam can be aimed
at a
specific target and used to initiate a response, which would provide real-time
identification of the subject target, as well as any number of other data
elements. In
addition, the system is capable of accurately determining the range between
the
interrogation unit and the target. The equipment required by the target
consists of a
simple transponder capable of transmitting the required data via a small stub
antenna. The
system is capable of operating at ranges up to 25 kilometers with a signal
power of 0.75
watts with no danger to operator or other human or animal life.
One application of this technology would be for reading electric meters. The
meter reader would be equipped with an interrogation unit. When a valid
interrogation
signal from the interrogation unit is sensed by the meter, the meter would
respond with
the meter identification number and the current reading of the electricity
used. The
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interrogation unit would record the data, along with the current time and date
of the
reading. Given an appropriate location of the meter, the entire operation
could be
conducted while the meter reader remained in a car.
5. Airlines: Currently, airlines must rely on the airport control tower to
give
them an estimate of when any given flight is expected at the gate. Depending
on the
workload of the control tower, this communication can often be sporadic and
untimely.
At least one major airline is looking for its own independent communication
system that
would become operative between the gate and the flight-specific pilot at about
15 miles
from the airport, allowing the airlines not to have to be reliant on an often
overloaded
control tower. The ability to know a more precise time of arrival of a given
flight will
increase the efficiency of service provided to airline users, and will result
in a significant
cost savings to the airline.
6. Automatic Teller Machines (ATM): While ATM's are everywhere in
the U.S., one does not typically find them in the numerous developing
countries. A highly
reliable, error-free, phone line is essential to ATM operations and such a
line is not
normally found in developing countries. However, a communication system based
on the
present invention could meet the need for a highly reliable, error-free,
wireless,
communications medium relaying information between ATM's and the clearing
bank, very
reliably and in a very secure mode.
7. Medical, Educational; and Other Developing Country Applications:
Communication from the more urbanized areas to the more remote areas in a
developing
country has been a long-standing problem. Ministers of Education often wish
that
educational programs designed in urban areas could be easily accessed by
remote area
schools. A point-to-multipoint communication system based on the present
invention
would make it possible to beam educational programs into numerous remote areas
in
voice or video mode, thus enhancing the quality of remote area education.
In developing countries, there are numerous remote area health clinics that
are
entirely severed from the more advanced medical knowledge that exists in
urbanized
areas. Often, these remote area clinics are staffed by capable medical
technicians who
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could save numerous lives if they had better information. As with educational
programs,
an efficient communication system would give the remote clinics instant and
reliable
communications with the urban medical center in either data, voice, or video
mode. Vital
signs and other medical information could instantly be sent to the urban
medical center for
analysis, a treatment decided upon, and the information beamed back quickly to
the
remote clinic.
8. Backbone Link for Cellular Regions: Currently, cellular regions are
linked together either by a microwave tower system supported by often
unreliable,
expensive radios and/or satellites. One base station based on the present
invention with
20 locations engineered into it can displace 280 microwave tower antennas and
280 radios
and 28 towers, resulting in a significant cost savings, while making it
possible to avoid
using expensive satellites, and passing on significant savings to consumers.
Moreover,
such a system would be more reliable and much less costly to maintain.
The embodiments shown and described above are only exemplary. We do not
claim to have invented all the parts, elements, or steps described. Various
modifications
can be made in the construction, material, arrangement, and operation, and
still be within
the scope of our invention.
The restrictive description and drawings of the specific examples above do not
point out what an infringement of this patent would be, but are to enable one
skilled in the
art to make and use the invention. The limits of the invention and the bounds
of the
patent protection are measured by and defined in the following claims.
